<template>
  <div class="box">
    <div class="pagination">
      <button :disabled="pageNo == 1" @click="$emit('getPageNo',pageNo-1)">上一页</button>
      <button v-if="startAndEndPage.start > 1" @click="$emit('getPageNo',1)" :class="{active:pageNo==1}">1</button>
      <button v-if="startAndEndPage.start > 2 ">···</button>
  
      <button v-for="(page,index) in startAndEndPage.end" :key="index" v-if="page >= startAndEndPage.start" @click="$emit('getPageNo',page)" :class="{active:pageNo==page}">{{page}}</button>
      
      <button v-if="startAndEndPage.end < totalPage-1">···</button>
      <button v-if="startAndEndPage.end < totalPage" @click="$emit('getPageNo',totalPage)" :class="{active:pageNo==totalPage}">{{totalPage}}</button>
      <button :disabled="pageNo == totalPage" @click="$emit('getPageNo',pageNo+1)">下一页</button>
      <button style="margin-left: 30px">共 {{total}} 条</button>
    </div>
  </div>
    
  </template>
  
  <script>
    export default {
      name: "Pagination",
      props:["pageNo","pageSize","total","continues"],
      computed:{
        // 总页数
        totalPage(){
          // 向上取整
          return Math.ceil(this.total/this.pageSize)
        },
        startAndEndPage(){
          let {pageNo,totalPage,continues}  = this;
          let start = null;
          let end = null;
          // 不正常 - 总页数 < 连续页码
          if(totalPage<continues){
            start = 1;
            end = totalPage;
          }else{ 
            // 正常情况 - 总页数 > 连续页码
            start = pageNo - parseInt(continues/2);
            end = pageNo + parseInt(continues/2);
            if(start < 1 ){
              start = 1;
              end = continues;
            }
            if(end>totalPage){
              end = totalPage;
              start = totalPage - continues +1;
            }
          }
          return {start , end}
        }
      }
    }
  </script>
  
  <style lang="less" scoped>
  .box{
    width: 100%;
    .pagination {
      text-align: center;
      button {
        display: inline-block;
        margin: 0 5px;
        background-color: #f4f4f5;
        color: #606266;
        outline: none;
        border-radius: 2px;
        padding: 0 4px;
        vertical-align: top;
        display: inline-block;
        font-size: 13px;
        min-width: 35.5px;
        height: 28px;
        line-height: 28px;
        cursor: pointer;
        box-sizing: border-box;
        text-align: center;
        border: 0;
  
        &[disabled] {
          color: #c0c4cc;
          cursor: not-allowed;
        }
  
        &.active {
          // cursor: not-allowed;
          background-color: #409eff;
          color: #fff;
        }
      }
    }
  }
  </style>